A state-of-the-art test equipment for characterization of advanced rheological materials

磁流变材料是一种可以利用外加磁场控制其流变行为的先进材料。磁流变材料可以是液体状态（磁流变流体）或固体状态（磁流变弹性体）。磁流变液通常由微米级的磁性极化颗粒（通常是羰基铁颗粒）组成，分散在矿物或硅基油等载体介质中。当暴露在磁场中时，这些磁偶极子沿着磁通量线排列，导致磁流变液从自由流动的粘性流体变为半固体，其屈服强度在毫秒量级可控。磁共振流体也可以通过毛细作用被限制在吸附性基质中，如海绵，以形成磁共振流体泡沫。磁流变弹性体是一种类似橡胶的材料（磁性颗粒悬浮在固体聚合物介质中），其模量可以自适应控制。磁共振材料在电子控制和机械系统之间提供简单、安静和快速响应接口的能力，使其成为新一代高带宽半有源器件的有吸引力的材料，可有效地用于提高不可预测环境变化下自适应结构系统的性能。MR材料可以有效地用于控制振动和结构噪声在宽频率范围内，从而允许设计下一代地面，航空航天和海上车辆，这些车辆具有成本效益和可靠性，同时满足乘客舒适度标准。为了有效地设计这些基于核磁共振的自适应结构，对核磁共振材料在不同外加磁场、激励频率和振幅以及温度下的动态行为的基本理解是至关重要的。考虑到这一点，所提出的设备需要对所有类型的MR材料在不同强度的磁场和不同的外部激励下在屈服前和屈服后区域的行为进行基础和系统的研究。所要求的磁流变仪是一种独特的设备，用于表征磁流变材料在宽范围内的激励频率和振幅，以及外部均匀磁场强度可达1特斯拉的温度下的行为。利用该装置可以研究磁流变材料的线性和非线性粘弹性以及屈服后区域的粘塑性行为。这将最终导致本构模型的发展，该模型可以准确地表征磁共振材料在不同工作区域的流变行为，从而可以有效地用于在不可预测的外部激励下对新型基于磁共振的自适应结构进行建模。

Magnetorheological (MR) materials are advanced materials whose rheological behavior can be controlled using the applied magnetic field. MR materials can be in liquid (MR fluids) or solid (MR elastomers) states. MR fluids are typically composed of micron-sized magnetically polarizable particles (typically carbonyl iron particles) dispersed in a carrier medium such as mineral or silicone based oils. When exposed to a magnetic field, these magnetic dipoles align themselves along the lines of magnetic flux causing the MR fluid to change from a free-flowing viscous fluid to a semi-solid with controllable yield strength in the order of milliseconds. MR fluids can also be confined in an absorbent matrix such as sponge by capillary action to form MR fluid foams. MR elastomers are rubber-like materials (magnetic particles are suspended in a solid polymeric medium) whose modulus can be adaptively controlled. The ability of MR materials to provide simple, quiet and rapid-response interfaces between electronic controls and mechanical systems have made them attractive materials for new generation of high bandwidth semi-active devices which can be efficiently used to improve the performance of adaptive structural systems under unpredictable environmental changes. MR materials can be effectively utilized to control vibration and structure-born noise in wide range of frequencies and thus allow to design next generation of ground, aerospace and marine vehicles which are cost-effective and reliable while meeting the standards for passenger comfort. To effectively design these MR-based adaptive structures, fundamental understanding of the dynamic behaviour of MR materials under varying applied magnetic field, frequency and amplitude of excitations as well as temperature is of paramount importance. Considering this, the proposed equipment is needed to conduct fundamental and systematic study on the behavior of all types of MR materials under varying intensities of magnetic field and varying external excitations in both pre-yield and post-yield regions. The requested magneto-rheometer is a unique device to characterize the behavior of MR materials under wide range of excitation frequencies and amplitudes, and temperature under the application of external uniform magnetic field intensities which can reach up to 1 Tesla. The linear and nonlinear viscoelastic properties of MR materials as well as their viscoplastic behavior in post-yield region can be investigated using the proposed equipment. This will eventually lead to development of constitutive models that can accurately characterize the rheological behavior of MR materials in different operating regions and thus can be effectively used in modeling of novel MR-based adaptive structures under unpredictable external excitations.